THE BEHAVIOR OF THE PHANTOM LARV.E OF 

 CORETHRA PLUMICORNIS FABRICIUS. 



BY 



E, H HARPER. 



(From the Zoological Laboratory of Northwestern University, Evanston, 111.) 

 With Five Figures. 



This paper describes some features of the behavior of the larvae 

 of Corethra plumicornis Fabricius var. Americana, one of the 

 short-beaked mosquitoes. Some observations upon the pupae 

 are included. The larvae of Corethra have attracted much atten- 

 tion among naturalists. They have been called the phantom 

 larvae on account of their transparency. They are of predatory 

 habit, lying in wait and feeding upon small Crustacea, Culex, etc. 

 The clear, open water is their preferred habitat. The writer has 

 found them in great numbers in a pond where predatory aquatic 

 insects abounded. Their daily depth migrations under the com- 

 bined influence of light and gravity are a prominent feature of 

 their reactions. 



Their behavior is modified in correlation with their trans- 

 parency, the absence of appendages, and their air sacs. Their 

 transparency secures them immunity. Their relation to the inor- 

 ganic environment is largely automatized through the air sacs. 

 They are thus enabled to maintain their position, through the 

 static function of the air sacs, at any level adapted to their physi- 

 ological state. The air sacs also serve a purpose dynamically 

 in producing certain automatic movements. There are two pairs 

 of these, anterior and posterior, through which the specific gravity 

 may be altered. Their immunity is associated with a lying-in- 

 wait habit, with discontinuous movements of intensive rather than 

 extensive type. The absence of appendages, besides being the 

 cause of the absence of certain familiar reactions (thigmotropic), 

 is further associated with an unconventional type of locomotion 

 and orientation to stimuli, which invites comparison with the 

 current explanations of the tropisms. 



